A large fire has broken out at Essar Oil UK’s Stanlow oil refinery, which processes around a sixth of the country’s petrol needs.
The Cheshire Fire Service confirmed it is in attendance at Ellesmere Port.
All staff have been evacuated.
It is believed the fire broke out within a manufacturing building in the plant.
Owners Essar Oil say the refinery plays a key role in the UK economy, supplying 16% of all road transport fuels.
More than 900 staff are emoloyed at the site, which processes around 200,000 barrels of oil per day.
The Cheshire fire service issued a statement: “Firefighters are liaising with onsite staff and the incident is confined to the site.
“Crews are using a ground monitor and a handheld monitor to extinguish pockets of fire.
“Crews are liaising with the Environment Agency and are managing the water being used at the scene.”